Because of the way the XenForo JS is compressed, automated JS minifiers (and YSlow/Google Page Speed) report that it can be compressed further. Actually minifying the files further with default settings breaks the JS, though - I haven't yet found a way around that.

I don't have cache enabled through the config file, nor do I have the minify enabled from acp. This particular JS file does not get flagged when do a speed test for xenforo. I do get it for cliptheapex with the exact same string. So doesn't look like unique to me.

Any JS or CSS file should have a unique version identifier appended to it for cache compatibility. If you look at the source for an XF page, you'll find them on all JS and CSS files. CSS files use the 'd' variable (date in unixtime), but it's the same thing.